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From "Jonathan Feinberg (JIRA)" <j...@apache.org>
Subject [jira] Updated: (OPENJPA-258) MetaDataInheritanceComparator is not transitive; C > B > A > C leads to out-of-memory crash in PCEnhancer
Date Tue, 12 Jun 2007 18:24:26 GMT

     [ https://issues.apache.org/jira/browse/OPENJPA-258?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jonathan Feinberg updated OPENJPA-258:
--------------------------------------

    Attachment: jpa-comparator-bug.zip

An eclipse/AJDT project. When built and run with AspectJ, will instrument the defective comparator
and fail fast on detection of cycle. Without AJDT, will run out of memory and die.

> MetaDataInheritanceComparator is not transitive; C > B > A > C leads to out-of-memory
crash in PCEnhancer
> ---------------------------------------------------------------------------------------------------------
>
>                 Key: OPENJPA-258
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-258
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: jpa
>    Affects Versions: 1.0.0
>         Environment: Sun JDK 5, Sun JDK 6
>            Reporter: Jonathan Feinberg
>            Priority: Blocker
>         Attachments: jpa-comparator-bug.zip
>
>
> Comparisons done by MetaDataInheritanceComparator are not transitive. It is possible
to have classes A, B, and C such that the comparator simultaneously reports that A > B,
B > C, and C > A. Under certain unlucky conditions, this causes the SortedTree holding
the metadata resolution buffer to become confused during Red-Black fix, such that it can retrieve
a certain element, but not delete it. The "processed" list then grows until heap is exhausted.
> In the enclosed sample project, 
> A < B by name
> B < C by assignable promary key field
> C < A by "levels" from base class (Object)
> If you import the enclosed eclipse project into an AspectJ-enabled eclipse, and refer
the AspectJ compiler to an OpenJPA jar file, you'll get the following output:
>   bug.B > bug.A
>   bug.C > bug.B
>   bug.A > bug.C
>   Cycle detected: 
>   bug.A > bug.C > bug.B > bug.A
> The project will work outside of AspectJ, and will exhibit the out of memory condition
described above.
> I acknowledge that the enclosed persistence.xml file is not kosher, in that it doesn't
list all classes to be instrumented. My own project, affected by this bug, has a correct persistence.xml
file. I had to work hard to contrive a simple example, as the order in which classes are buffered
affects the appearance of the bug.
> There is no work-around that I know of. I don't believe that the comparator's semantics
are well-defined.

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